Three-Dimensional Modeling of Suspension Plasma Spraying Process

In a DC plasma torch, the arc root is constantly moving on the anode surface which results in voltage fluctuations. Because the arc current remains constant, the net result will be fluctuations in plasma power and, hence, in temperature and plasma flow velocity. This is undesirable since it affects the consistency of heating, accelerating, and trajectories of the injected particles. Understanding the effect of such fluctuations on heating and melting of the injected particles in suspension plasma spraying process is the objective of this work.

In this study, first the plasma fields, including arc reattachment process, is simulated using a three-dimensional unsteady magneto-hydrodynamic model. The plasma gas is pure argon. After modeling the oscillating plasma jet, the results are applied to analyze the effect of arc fluctuations on the suspension droplets trajectory, temperature and velocity. Suspension droplets, formed of ethanol and Yttria Stabilized Zirconia (YSZ, 8 wt. %) sub-micron particles, are considered as multicomponent droplets and tracked using a two-way coupling Eulerian-Lagrangian method. Moreover, droplets breakup is modeled by Kelvin-Helmholtz Rayleigh-Taylor (KHRT) breakup model. After the completion of suspension droplets breakup and evaporation, the sprayed particles are tacked through the domain to obtain the in-flight particles properties.